2 Answers
2

Many Scheme implementations have support for image files. The R5RS standard, as written, does not. I suggest using Racket, where you can use, e.g.,

(require 2htdp/image)
(bitmap/file "/path/to/foo.jpg")

In fact, there are many parts of building a game that are not going to fit well under the R5RS umbrella. I'm afraid you're almost certainly going to have to pick an implementation, and use features that lie outside of the standard.